optimx: Expanded Replacement and Extension of the 'optim' Function

Provides a replacement and extension of the optim()
function to call to several function minimization codes in R in a single
statement. These methods handle smooth, possibly box constrained functions
of several or many parameters. Note that function 'optimr()' was prepared to
simplify the incorporation of minimization codes going forward. Also implements some
utility codes and some extra solvers, including safeguarded Newton methods.
Many methods previously separate are now included here.